The present invention relates to inertia responsive seat belt retractors. More specifically, the present invention relates to inertia responsive retractors utilizing a hanging pendulum as the inertia sensor.
The hanging pendulum type inertia responsive seat belt retractor is a well-known seat belt retractor which is being used for occupant restraint in modern vehicles. In general, the hanging pendulum type retractor includes a pendulum saddle which has a hanging or seating surface from which is suspended a pendulum. These pendulums have a weight body which includes a neck that is connected to a head portion. The head portion seats or is hung from the pendulum saddle with the weight body being suspended vertically therefrom. During normal vehicle operation, the weight body remains suspended directly or vertically below the pendulum head. When the vehicle is subjected to extreme changes in velocity, such as the extreme deceleration encountered during accidents, the weight body swings away from its vertical position suspended below the pendulum saddle. As the weight body swings, the head portion nutates or is rocked about its seating engagement with the pendulum saddle. This nutation or rocking motion, lifts a suitably placed pawl to engage a ratchet wheel and thereby lock the retractor against unwinding movement. In this manner, the retractor belt wheel is freely rotating against its spring bias at all times except when the weight body swings in response to changes in velocity and thereby actuates the pawl into locking engagement.
An important factor in proper operation of hanging pendulum type retractors is the proper mounting of the pendulum saddle so that the pendulum may be hung vertically without rocking the pendulum head to cause inadvertent actuation of the locking pawl. Many different mechanisms have been devised to provide a self-adjusting means to compensate for possible differences in the pendulum saddle mounting orientations. These devices are characterized by complicated pivot assemblies utilizing ball bearings and universal fittings. Exemplary of such prior art attempts to provide a self-adjusting pendulum sensor assembly is U.S. Pat. No. 3,938,755 issued to Stephenson et al. on Feb. 17, 1976. The Stephenson patent discloses a self-adjusting pendulum sensor assembly employing a trunnion assembly which is adapted to pivot in two directions upon its swivel axis with reference to the pendulum saddle. Two other prior art patents (U.S. Pat. No. 3,938,754 and U.S. Pat. No. 3,901,461) both also issued to Stephenson et al., similarly disclose self-adjusting pendulum-type inertia sensitive devices based upon pivotal mounting of the pendulum assembly to allow pivoting to various compensating positions when the pendulum saddle is tilted to various mounting orientations.
Another attempt at providing a self-adjusting device to compensate for different pendulum saddle orientations is U.S. Pat. No. 4,077,584 issued to Lafont on Mar. 7, 1978. The Lafont patent is not based on the hanging pendulum but relies on the rolling of a ball bearing about a dished surface during changes in velocity to operate a lever which in turn operates a pawl to lock a belt reel. This device is a departure from the standard pendulum inertia sensor assembly and although providing a means for compensating for different pendulum saddle orientations, the need for a ball bearing and associated bowl or dish and socket joints is not as desirable as the simple and reliable hanging pendulum type inertia sensor assembly.
Although the above cited self-adjusting pendulum inertia sensor assemblies are suitable for their intended purpose, they still include many more complicated parts than the initial standard pendulum inertia sensor assembly. In the standard pendulum assembly, the pendulum head is mounted at right angles to the pendulum neck with the pendulum neck and weight body having a center of gravity directly below the center of the pendulum head. When the pendulum saddle is horizontally mounted, the pendulum head seats on the pendulum saddle with the weight body suspended vertically below.
It would be desirable to provide an inertia sensor assembly having the simplicity and reliability of the standard type pendulum inertia sensor assembly while at the same time including features allowing non-horizontal orientation of the pendulum saddle.